In today's society, electrical and electronic devices are plentiful. For example, televisions, personal computers and cellular phones can be found as common household items in many people's homes. Many, or perhaps most, of these devices include application specific integrated circuits (ASICs). ASICs provide customized functionality for different devices. However, the functionalities of these ASICs have becoming increasingly complex, requiring million and even billions of transistors to be integrated to form a complete ASIC chip.
ASICs are most commonly realized in the topmost part of single crystalline silicon wafers. Signal routing for connecting different parts of an ASIC circuit on such silicon wafers (both for digital and analog circuitry) is currently accomplished by using electrical wiring, e.g., patterned onto the silicon wafer. For example, multiple metal layers deposited on top of the ASIC structure can be patterned to form individual connections between transistors and functional blocks as desired.
In such ASICs, integrated circuits or other “on-chip” devices, the capacitance associated with each signal wire loads the feeding circuits with an impedance load that increases as a function of clock frequency. Thus, the dynamic dissipated power of the signal line also becomes higher with frequency according to the function:Pdiss=CLV2DDf  (1)where:    Pdiss=dissipated power,    CL=capacitance of the signal line connected to the feeding circuit,    VDD=supply voltage, and    f=clock frequency.The packing density in such devices increases as the width of the metallized traces or signal lines goes down, resulting in higher and higher dynamic power dissipation per unit of chip area, thereby limiting the usable clock frequency. This is the reason why the steady and periodic increase in the clock frequency for digital circuitry has now come to a halt for digital processors.
One solution that has been discussed to overcome this problem is to replace, as much as possible, electrical signals with optical signals on-chip. However this raises the issue of how to convey optical signals on, e.g., a silicon chip. Traditionally, optical signals are conveyed in, for example, optical fibers between optical transmitters and optical receivers. However, classical optical fiber arrangements using e.g., drawn silica fibers, are not compatible with the semiconductor manufacturing processes used to fabricate ASICs, other integrated circuits and the like.
Accordingly, systems, methods and devices for providing an on-chip optical waveguide would be desirable.